Plate Tectonics Flashcards
What did scientists used to think about the Earth’s wrinkles?
They were caused by the shrinkage of the surface as it cooled down after the Earth was formed.
What is Alfred Wegeners theory?
Continental drift.
What is Alfred Wegener come across?
Some work listing the fossils of very similar plants and animals which had been found on opposite sides of the Atlantic ocean.
Alfred investigated further, what did he find?
Found other cases of very similar fossils on opposite sides of oceans.
Initially what was the accepted explanation for fossils being found on opposite sides of the ocean?
That there was once land bridges linking the continents - so animals had been able to cross.
The bridges have ‘sunk’ or been covered over since.
What else did Wegener notice?
That the coastlines of African and South Africa seemed to match like the pieces of a jigsaw.
He wondered if these 2 continents had previously been 1 continent which then split.
After noticing the African coastlines matched like jigsaws, he looked for more evidence, what did he find?
There were matching layers in the rocks in different continents.
Where had a lot of fossils been found?
In the wrong places.
eg fossils of tropical plants had been found in Arctic islands, where the climate would have clearly killed them off.
What happened when Wegener thought he had enough evidence about continental drift?
In 1915 he published his theory of ‘continental drift’.
What did Wegener say in his theory?
That 300 million years ago, there has been just one ‘super continent’.
The landmass Pangaea broke into smaller chunks which moved apart.
These chunks are out modern day continents.
The reaction from other scientists was very what?
Hostile.
It wasn’t very convincing.
What did Wegener think about the continents?
That they were ploughing through the sea bed.
Their movement caused by tidal forces and Earth’s rotation.
What did one scientist calculate?
That the forces needed to move the continents like this would have also stopped the Earth’s rotation.
Wegener made inaccurate data in his calculations, what did this cause him to do?
Make wild predictions about how fast the continent ought to be moving.
A few scientists did believe him but most of them didn’t see any reason to, give a reason why?
He wasn’t a ‘proper’ geologist, he studied astronomy.
